The present invention relates to object detection systems, and more particularly to underwater directional object detection systems.
In detection of the distance or direction of a distant object from a sensor system capable of receiving signals therefrom, such as in an underwater sonobuoy system for submarine detection, the sensor system generally is not oriented towards a known reference such as magnetic north. When the sensor system transmits information to a distant receiver, lack of such a reference makes it difficult for the distant receiver to properly analyze the information received to produce correct information concerning the location of the detected object. Previous methods of correcting the sonobuoy signals to magnetic north have involved including a separate signal from an on-board compass in the signals transmitted to the receiver. The resulting signals received at the distant receiver are then processed there. In such a situation, the transmitted compass signal would be subject to distortion, interference and noise in the medium. Furthermore, in such systems, the transmitted signals would not be directly applicable to a computer type processor, and would require processing and conversion to be so directly applicable. In addition, such systems do not lend themselves to built-in testing of the individual sensor/transmitter system, since the compass correction is not performed until signals are processed at the receiver. This makes it difficult to determine whether the sensor/transmitter system is malfunctioning, which such system (if several are being used) is malfunctioning if any, or whether the problem lies in the distant receiver.